The epidemic of isothiazolinone sensitivity documented in Europe is now in North America, according to a recent study. During the last decade, the use of methylisothiazolinone (MI) at higher concentrations in both leave-on and rinse-off products has significantly increased. Furthermore, patch testing with only methylchloroisothiazolinone (MCI)/MI 0.01% aqueous (aq) will miss approximately half of isothiazolinone allergy cases, whereas testing with only MI 0.2% aq will miss approximately 10% of isothiazolinone allergy cases. At 13 centers in North America, 4,860 patients were patch tested in a standardized manner with a series of 70 allergens, including MCI/MI 0.01% aq and MI 0.2% aq. Researchers found:
- 305 patients (6.3%) had a positive reaction to MCI/MI; this is a significant increase from the previous cycle (5.0%, 2011-2012).
- 521 patients (10.7%) had a positive reaction to MI.
- These 2 isothiazolinones were among the most common preservative allergens in the 2013 to 2014 cycle; 11.9% of patch-tested individuals were allergic to 1 or both isothiazolinones.
- Individuals with MCI/MI and MI allergy were significantly more likely to have occupationally related skin disease and hand dermatitis.
Zirwas MJ, Hamann D, Warshaw EM, et al. Epidemic of isothiazolinone allergy in North America: Prevalence data from the North American Contact Dermatitis Group, 2013-2014. [Published online ahead of print May 1, 2017]. Dermatitis. doi:10.1097/DER.0000000000000288.
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